Duration Complement: Interval After Action Completion
数量补语5（动词+时量补语）：表示动作结束后到某个时间点的间隔时间
Express how much time has elapsed since an action was completed
Place the duration after the verb (and its object if any), then add 了 at the end of the sentence. This indicates how much time has passed since the action occurred.
The final 了 is essential — it signals that the time has been accumulating up to the present moment. Without 了, the sentence describes a duration of action rather than elapsed time since the action.
Lesson Targets
Podcast
Podcast: Duration Complement: Interval After Action Completion (数量补语5（动词+时量补语）：表示动作结束后到某个时间点的间隔时间)
Listen to Jason & Amy explain the 数量补语5（动词+时量补语）：表示动作结束后到某个时间点的间隔时间 pattern
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Understanding 数量补语5（动词+时量补语）：表示动作结束后到某个时间点的间隔时间
This structure answers the question "how long ago?" or "how long has it been since...?" In English we say "They have been in China for two months" or "It has been a week since he went to Beijing." In Chinese, you state the action, then the time that has elapsed, and end with 了: 他们来中国两个月了. The crucial difference from the previous grammar point (GP-51) is that here the action itself is already completed — you are measuring the gap between that completion and now. The final 了 is what makes this work: it tells the listener the clock is still ticking. Compare: 他去北京一个星期 (neutral statement) vs. 他去北京一个星期了 (it has been a week and the situation continues). This pattern is indispensable for talking about life milestones, moves, relationships, and elapsed time.
Key Points
- The action is already completed; you are measuring time since that moment.
- Final 了 is required — it marks the continuing relevance of the elapsed time.
- Subject + verb + (object) + duration + 了: 他们来中国两个月了.
- This is different from the action-duration complement (GP-51) which measures how long an action lasted.
- Common verbs: 来 (come), 去 (go), 结婚 (marry), 毕业 (graduate), 搬 (move), 离开 (leave).
- You can ask: 你来中国多长时间了？(How long have you been in China?)
- The subject is often in the new location or new state as a result of the completed action.
This pattern frequently comes up in small talk with Chinese people. One of the first questions you might hear is 你来中国多长时间了？(How long have you been in China?). Being able to answer naturally — 我来中国半年了 — will make a great first impression.
Key Vocabulary
Example Sentences
他们来中国两个月了。
They have been in China for two months (since they came).
哥哥去北京一个星期了。
It has been a week since my older brother went to Beijing.
我父母结婚二十年了。
My parents have been married for twenty years.
她毕业三年了。
It has been three years since she graduated.
我搬到这个城市五年了。
I have lived in this city for five years (since I moved here).
他离开公司半年了。
It has been half a year since he left the company.
爷爷去世十年了。
It has been ten years since grandfather passed away.
Common Mistakes
The final 了 is essential. Without it, the sentence does not convey the sense of time elapsed up to the present.
Do not add 了 right after the verb in this pattern. Only the sentence-final 了 is used to mark the elapsed interval.
In the interval pattern, 了 only appears at the end of the sentence. Adding 了 after the verb changes the meaning.
Practice Exercises
Tips & Tricks
Think of the final 了 as a "still ticking" marker — the time is accumulating up to right now.
Compare carefully: 我学了两年中文 (I studied for two years — maybe stopped) vs. 我来中国两年了 (I have been in China for two years — still here).
This pattern works best with one-time actions: coming, going, marrying, graduating, moving.
Practice with your own life milestones: when you started school, moved cities, or began learning Chinese.
Homework
Write eight sentences about important events in your life or the lives of people you know, stating how long ago each event happened. Use verbs like 来, 去, 搬, 结婚, 毕业, and 离开.